program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  PointX, PointY : array of Integer;
  N : Integer;
  Sign : Integer;
  BadFlag : Integer;
  I : Integer;


function ScalarProduct(A, B : Integer) : Integer;
begin
   ScalarProduct := PointX[A] * PointX[B] + PointY[A] * PointY[B];
end;


begin
  read(N);
  BadFlag := 0;
  SetLength(PointX, N);
  SetLength(PointY, N);
  for I := 0 to N - 1 do
    read(PointX[I], PointY[I]);
  Sign := ScalarProduct(0, 1) * ScalarProduct(0, 2);
  for I := 1 to N - 1 do
      If(((ScalarProduct(I, I + 1) * ScalarProduct(I, I + 2)) > 0) xor (Sign > 0)) then
        BadFlag := 1;
  if(BadFlag = 1) then
     write('Yes')
  else
     write('No');
  Readln;
  Readln;
  Readln;
end.
